/**
 * This script adds a [toggle visibility] link to level 2 section headers.
 * The link does what it says on the tin.
 * No promise of accuracy or non-brokenness made.
 * Tested in Vector and Monobook. Last test: 2018-07-12.

 * To install, add the following to your commmon.js or skin.js:

 mw.loader.load('//en.wikipedia.org/w/index.php?title=User:BethNaught/hideSectionDesktop.js&action=raw&ctype=text/javascript'); // Backlink: [[User:BethNaught/hideSectionDesktop.js]]

 * Author: [[User:BethNaught]]
 
 * Category: [[Category:Wikipedia scripts]]
 */

/** global $ */

$(document).ready( function() {
	// Helper functions
	function _toggleVisibility(elt) {
		if (elt.style.display == "none") {
			elt.style.display = "";
		} else {
			elt.style.display = "none";
		}
	}
	function _createToggleVisibilityLink(sectionID) {
		// Create HTML
		var out = document.createElement('span');
		out.classList.add('mw-editsection');
		
		var left = document.createElement('span');
		var right = document.createElement('span');
		left.classList.add('mw-editsection-bracket');
		right.classList.add('mw-editsection-bracket');
		var leftBracket = document.createTextNode("[");
		var rightBracket = document.createTextNode("]");
		left.appendChild(leftBracket);
		right.appendChild(rightBracket);
		
		var center  = document.createElement('a');
		center.classList.add('nonimage');
		center.title = 'Toggle visibility: ' + sectionID;
		var centerText = document.createTextNode("toggle visibility");
		center.appendChild(centerText);
		center._classToToggleSelector = '.bn-hidesection-' + sectionID;
		
		out.appendChild(left);
		out.appendChild(center);
		out.appendChild(right);
		
		// Event listener
		center.addEventListener("click", function() {
			$(this._classToToggleSelector).each( function() {
				_toggleVisibility(this);
			});
		});
		return out;
	}
	
	// BEGIN WORKFLOW
	// This holds the stuff that comes from wikitext, and that only
	var parserOutput = document.getElementsByClassName('mw-parser-output')[0];
	
	if (parserOutput) {
		// Initialise loop variables
		var classifying = false;
		var sectionID = 0;
		var temp_a, currentChild;
		var loopLength = parserOutput.children.length;
		
		// Loop over children adding necessary stuff
		for (var i = 0; i < loopLength; i++){
			currentChild = parserOutput.children[i];
			if (currentChild.nodeName.toLowerCase() == "h2") {
				classifying = true;  // all subsequent elements need modifying
				sectionID += 1;
				temp_a = _createToggleVisibilityLink(sectionID);
				currentChild.appendChild(temp_a);
			} else if (classifying) {
				currentChild.classList.add('bn-hidesection-' + sectionID);
			}
		}
	}
});